Merge r1526079 from branch-2 to branch-2.1-beta for YARN-1214. Register ClientToken MasterKey in SecretManager after it is saved (Jian He via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1526081 13f79535-47bb-0310-9956-ffa450edef68